Gear-cutting machine.



T. PAWCUS.

GEAR CUTTING MACHINE.

PPLIGATION FILED JAN.11. 1912.

Patented Jan. *n 1913.

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APPLIGATION FILED 111.11.11. 1912.

1,049,315@ Patented Jan.7,1913.

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To all w/io'm. it may concern:

Be it known that Trioiiiis Fawcos, a

- resident of Pittsburgh, in the county of Al-v means whereby the speedof one of the hobs,

leglieny and State of Pennsylvania, have in-4 vented a new and usefulImprovement in' Gearutting Machines, of which the following is a `full,clear, and exact description,

reference being hadto the accompanying' dra-wings, forming part of thisspecification, in which- `Fig-ure 1 is a plan View of a machineembodying my invention; Fig. 2 is a side elevat-ion of. a portion of themachine; and Fig. is a side view of a portieri of the machine lookingfrom the opposite side.4

'The present invention isvan improvement upon the gear-cutting machinedescribed and claimed in my application, Serial No.'

613,885,'led March 11, 1911, and which is particularly aadapted forclit-ting double helical gears. The machine described and claimed inthat application comprises a rotatable blank support, means forrevolving the same, a pair of rotary cutting hobs mounted on separateaxes and arranged to act simultaneously upon the revolving gear blank,together with means for feeding both hobs in the saine direction and ina line parallel to' 'the axis of the blank. hobs is arranged to cut fromone edge of the blankvtoward the center, while, the other cuts from thecentral portion of the blank toward the opposite edge. inasmuch as thetwo hobs are working simultaneously upon the blank, each formingone-half of a double helical tooth, it was necessaryin the maw chine ofthe said application to provide will be retarded relatively to the speedof the rotating blank, and whereby the speed `of the otherA hob will beadvanced with rei' erence to the speed of the rotating blank. In themachine specically shown and described in lsaid application, for thepurpose of obtaining this variation in the speed of the hobs relativelyto the speed of the blank, I -prcvidean arrangement of differentialgears. i

The present invention relates 'to a machine which is generally similarto that of the said application, but is designed to, obviat-e the use ofthe differential gears and to provide other-means of simple andeffective character for obtaining such speed variation, thus doing awaywith considerable number Specification of Letters SEateiit.

Application filed January 11, 1912.

One of the i @Patented Jan. t', i913. serai ivo. emana of gears andgreatly simplifying the machine.

ln the accompanyingr drawings, the niiv ineral 2 designates the bedframe of the mariage 5, movable longitudinally on the bed'` of themachine in suitable Ways 6.

A designates a partially cut blank which ner and which is to have doublehelical teeth cut therein. I l 7 and S designate the two cutter hobshaving helical cutting teeth which mesh with the teeth which they out inthe blank, one of the hobs being right-handed and the other left-handed.The hob 7 is mounted upon the transverse shaft- 9, while the hob 8 ismounted on the transverse shaft 10, these two shafts being journaled oneabove another in suitable bearings on a vertically movable slide orcarrier 11, which .works on the vertical ways Provision is made, asindicated zit-13, whereby the bearings for the is secured `on the table3 in any suitable manshaft 9 may be adjusted to vary the distancebetween the centers of the two shafts 9 and 10, to suit different Sizedgear blanks. Theslide or carrier 1l is given its feed movenient by thevertical feed screw let, which enga-ges a nut portion 15, of the slideor cars riage. rlhe hob shaft 9 has at one end a gear wheel 9a, which isengaged and driven `by a pinion 9b, on an intermediate shaft 9,

which has a spiral gear 9., engaged and driven Yby a spiral gear 17, ona vertical shaft 18 at one side ofthe machine. The

hob cha-ft- 10 is diiiven through similar gears 10u and 10b and spiralgears 19 and 20, the latter being on a `vertical shaft 21, at theopposite side Vof the machine. Each of the shafts 18 and 21 carries abevel gear wheel 22 at the lower end for `engagement with acorresponding bevel gear on a transverse driving shaft 23. The Wormshaft 23 drives the two shafts 18 and 21 in opposite direction, so thatthe two hobs are driven inopposite directions. l j A The numeralBOdesignates a belt pulley ico which forms the main drive of 'the'machine.,

The. shaft of this-pulley carries the .'gelarf' wheel 31, which, throughthe gears 3 3,

the shaft 23, before described, and through tached thereto a gear wheelt/l, carried by a stub shaft 45, and meshing with the gear wheel 46.This gear 46 is'mounted on the transverse shaft 51, carrying a bevelgear pinion 52, which meshes with a bevel pinion 5l on the longitudinalshaft 55. The'shaft 55 has a threaded portion which is adapted to engageand actuate a nut 56 on the carriage 5. The shaft 51'also has a bevelpinion 58, meshing with a bevel pinion 59 on the feed shaftor screw 14,before referred to. Said shaft 51, therefore, through the shaft 55,forms a means for feeding the blank longitudinally of the machine andalso acts as a driving shaft for moving the cutter or hob carrier. Thetwo pinions 52 and 58 are loosely mounted on the shaft 51, andarearranged to be alternately connected therewith through suitable clutchmechanism not shown, but which is arranged to be controlled lthrough theoperation of a shifting rod 60, ha ving a collar 61, which is arrangedto be engaged b vthe carriage 5. This shifting rod alf-'o has aconnected member 62, provided with an adjustable collar 63, which isarranged to be engaged by the slide or carrier 1.1.

As thus tar described, the machine is generally similar to that of theprior application above I 'efferrlal lo, with die exception that the.vertical shafts 18 and 2t are not formed in sections with a.differential gear connection, as iu the said application. ln the presentmachine, each of said shafts is formed with a helical gro-'Jvc or keywayGil. which is engaged bv a key or feather in the hub of thecorresponding spiral gear 17 0r QI). It will be apparent. that as thescrew shaft 1-14 is actuated to feed the cutter carrier downwardly in adirection parallel to the axis of the blank A, the keys of the gears 17and 2O will be obliged to follow these helical grooves or keyways., andthat, inasmuch as said shafts 18 and i1 are rotating in oppositedirections, one lof the worms will be caused by this groove or keyway tohave its effective speed slightly increased relatively to the speed ofthe rotating blank; while the other worm will have its effective speedcorrespondingly retarded. This change `in the speeds of these two wormsfleets, of course, a correspoliiding change in ters relatively to theblanks, andthe result `is to cause the cutters t-o form teeth at t-heproper angle and pitch. Inasmuch as the angle and pitch of the teethalso vary for different gears, provision is preferably made for drivingthe shafts 18 and 2l at different speeds by the use of suitable changegears and driving connect-ions.

The operation, of the machine is as follows: The blank having beensecured in place onthe table 3 and the hobs 7 and 8 adjusted at adistance apart'suitable to the width of face of the gear to beeut, themachine is set in motion and the hobs and blankcaused to revolve attheir relative speeds, that is, .at the precise ratio which the numberof threads in each hob bears to the number of teeth to be cut in theblank. The shaft 56 is now put into operation to feed the blankforwardly into cutting-relation to the hobs, and this feed movementisallowed to proceed until the required depth of cut is reached. Theupper hob 7' is set to eut.

slightly below the center line on the edge of the blank, and the hob 8te cut approximately at the peripheral center of the blank. When theblank has been fed and the cutting operation has progressed until therequired' depth of cut is reached, the vertical feed is set in operationthrough the gear 59 and the screw 1-1.

lt will be readily understood that by the use of change gears at asuitable point in the train of gearing` described, both the rate of feedof the feed screw 14 and also the` time relation between the feed screwand the speed of the lspiral gears 17 and 19 may be varied. i

There is a definite relationbetween the pitch ofthe helix on thevertical shafts and the pitch of the hob, so that if the hob shafts weregeared positively to the vertical shafts, it would be necessary to havea different set (if-vertical shafts for every pitch. This is obviated bymaking the gears loo 9 and 9" change gears, whereby the relation betweenthe .speeds of the vertical shafts and the hobs may be varied, as thepitches vary. For example, assuming that for a given pitch and angle,even gears were necessary'at- 9 and 9b, for twice the pitch and the sameangle, the hobs would be twice the diameter of the former ones and gearsto secure a reduction of two to one, would be used at 9? and 9b. In'other words, the number of revolutions; would be reduced one-half, butsince the hob is twice as large, the'periphery speed remain'sthe same.

Instead of driving the two shafts 18 and 21.' in opposite directions,they may, of course, be driven in the same direction and havetheir-helixes of op )osite hand.

The numeral 565 esignatesa cutter which is arranged to make a cut inaline substantially parallel to the axis of the.

can not operate without ther feed and can not fail to operate with it,being substituted. There is such a small amount of movement that thereis practically no loss of motion through wear. Consequently, there islittle opportunity for errors and the work can be accurately done.

I do not wish to limit myself to the details of the machine as hereinshown and described, since it is obvious that various changes within thescope of the claims may be made therein Within-the spirit and scope ofmy invention; and that, so long as the machine embodies the essentialfeatures of t-he invention set forth in the appended claims, thisembodiment may differ Widely from the particular embodiment which I haveshown and described.

I claim:

1. ,In a machine for forming double helical gears, two rotary cutters,means for feeding said cutters in the same direction, and means fordriving the cutters at relatively different speeds, said meanscomprising gear mcmbers'and shafts for said members, said shafts havinghelical grooves or ways to be traversed by the gear members,substantially as described. l

2. In a machine for forming helical gears, two rotary cutters, means forfeeding said cutters in the same direction, and means for rotating thecutters at relatively different speeds, said means comprising gearmembers and oppositely driven driving shafts for said members upon whichthey are longitudinally movable, said shafts having helical grooves orways, and the feeding means being adapted to move said members on saidshafts, substantially as described.

3. In a machine for cutting helical gears', a rotary cutter, and drivingmeans therefor, said means comprising a shaft having a helical groove orway, and a gear member longitudinally movable on said shaft and having akey engaging said groove or way, substantially as described.

4. In a machine for cutting helical gears, a rotary cutter, and drivingmeans therefor comprising a shaft, agear Wheel movable longitudinally ofthe shaft, and feeding mechanism connected to the gear Wheel to move iton its shaft, with means for varying the speed of t-he gear relative toi the shaft as it is moved thereon, substantially as described.

5. In a machine for cutting helical gears, a rotary hob, driving meanstherefor com prising a shaft, a gear wheel movable longitudinally of theshaft, and fee-ding 1nechanism connected to the gear wheel to move it onits shaft, with means for varying the speed of the gear relative to theshaft as it is moved thereon, and means for varying the speed ofrotation of the hob for hobs of different diameters, substantially asdescribed. l

6. In a machine for cutting helical gears, a rotary hob, driving meanstherefor comprising a shaft, a gear wheel movable longitudinally of theshaft, and feeding mechaynism connected to the gear wheel to move it onits shaft, with means for varying the speed of the gear relativel to theshaft as it is moved thereon, and a gear connection between the saidgear wheel and the hob having a changeable element, substantially asdescribed.

In testimony whereof, I have hereunto set my hand. i

THOMAS FAWCUS.

